Adsorption of fluoride by the calcium alginate embedded with Mg-Al-Ce trimetal oxides

Enhanced fluoride removal with sequentially modified alginate biopolymer: Insights from mathematical and column models

This study investigates the use of brown algae-derived alginate biopolymer to improve fluoride (F-) removal in water treatment. It compares two modified alginate-based adsorbents: zirconium-crosslinked alginate (AZ) and a newly developed material created by combining ferric aluminosilicate laterite (FASL), a mining by-product, with alginate and crosslinking it with zirconium, called ALZ. Both AZ and ALZ were synthesized and characterized using SEM-EDX, FT-IR, TGA-DTA, XRD, XRF, and BET. Their ability to remove fluoride from aqueous solutions was tested, achieving over 70 % removal efficiency through process optimization with response surface methodology (RSM). The adsorption process followed the Langmuir isotherm and pseudo-second-order kinetics. Increasing temperature improved fluoride adsorption for both materials, with maximum capacities at 30 °C and 50 °C: 70.27 mg g-1 and 117.64 mg g-1 for AZ, and 170.14 mg g-1 and 410.81 mg g-1 for ALZ, respectively. Thermodynamic analysis confirmed the process was spontaneous across all temperatures. Mathematical modelling was also used to predict fluoride breakthrough. This research provides valuable insights for developing efficient methods to address fluoride contamination, with both industrial and drinking water samples tested. The synthesis process demonstrated environmental sustainability, with a low environmental-factor (E-factor) of 0.023, highlighting its eco-friendly nature.

Advances in structure designing and function tailoring strategy toward alginate-based hydrogels for efficient water remediation: A review

Alginate (mainly sodium alginate, SA), as a natural polysaccharide material, has been widely applied in water remediation due to its excellent biocompatibility, degradability, and high hydration properties. Alginate hydrogels exhibit high adsorption capacity, effectively removing heavy metal ions, dyes, antibiotics, phosphate ions, and other pollutants from wastewater. This review begins with a description of the chemical structure of sodium alginate and its physicochemical properties, followed by a detailed discussion of the preparation methods of alginate-based composite hydrogels, including physical and chemical crosslinking, emulsification, electrostatic complexation, self-assembly, ultrasound and microwave-assisted methods. Based on the different compositions of the composites, alginate-based composite hydrogels are classified into several types for the removal of specific pollutants. Moreover, the paper systematically summarizes the research progress of alginate-based composite hydrogels in adsorbing heavy metal ions, dyes, antibiotics, phosphate ions for application effects. Although alginate-based composite hydrogels demonstrate great potential in water remediation, challenges such as insufficient mechanical strength, poor regeneration ability, and low stability under extreme conditions still exist. Finally, the future development prospects of alginate composite hydrogels in the field of water remediation, as well as potential research directions to improve their adsorption performance, enhance their regeneration capacity, and improve their environmental friendliness are presented.

Synergistic Fluoride Adsorption by Composite Adsorbents Synthesized From Different Types of Materials—A Review

The reduction of fluoride concentrations in water is one of many concerns. Adsorption is the most widely used technology for fluoride removal and the center to development of adsorption technology is the improvement of adsorbents. This review classifies the typical fluoride removal adsorbents into four types: metal oxides/hydroxides, biopolymers, carbon-based, and other adsorbents. The exploitation of new materials and the synthesis of composite materials are two ways of developing new adsorbents. In comparison to the discovery of novel adsorbents for fluoride adsorption, research into the composite synthesis of different types of conventional adsorbents has proliferated in recent years. The traditional adsorbents used the earliest, metal oxides, can act as active centers in a wide range of applications for modifying and compounding with other types of adsorbents. This study emphasizes reviewing the research on fluoride removal by composite adsorbents synthesized from different types of metal-modified materials. Seven factors were compared in terms of material characterization, initial fluoride concentration, adsorbent dose, pH, temperature, reaction time, and maximum adsorption capacity. The modification of composite adsorbents is facile and the synergistic effect of the different types of adsorbents significantly improves fluoride adsorption capacity. Metal composite adsorbents are synthesized by facile coprecipitation, hydrothermal, or impregnation modification methods. The adsorption mechanisms involve electrostatic attraction, ion exchange, complexation, and hydrogen bonding. The fluoride adsorption capacity of composite adsorbents has generally improved, indicating that most modifications are successful and have application prospects. However, to achieve significant breakthroughs in practical applications, numerous issues such as cost, separation/regeneration performance, and safety still need to be considered.